Continuity mistake: At the end, as the doctor walks away from Alice after questioning her, she changes from looking up at him to looking down between shots. (01:22:45)
Continuity mistake: Watch the remains of the metal bar that sticks out of the building after Nemesis ripped it off to fight Alice. If you look at the point of the metal it is horizontal. When Nemesis is pushed onto it, it is vertical. (01:08:30)
Continuity mistake: When LJ shows his custom guns to the STARS, he opens his coat and pulls the tail behind his back. In the wide shot, his arms are out to the sides. (00:37:15)
Continuity mistake: When the Suburban is T-boned, it is replaced with an older 92-94 Suburban with the front end of a newer 00-04 Suburban installed in place of the older front end. Older model 6 spoke wheels are installed instead of the 00-04 wheels shown in previous scenes. In one of the shots towards the end of the sequence, a completely different 96-99 suburban is shown rolling over with five spoke wheels, and the scene is mirrored.
Continuity mistake: Early on a pallet is leaning against a building with nothing next to it as two star members are backing up shooting at zombies. About eight seconds later you see an aluminum tube standing in front of that pallet. It then comes and goes. (00:15:00)
Character mistake: Jill states that a 5 kiloton nuclear weapon will sanitise the city, however, such a yield is far too small to destroy the city. (00:42:00)
Revealing mistake: When Yuri gets bitten while the SWAT team, along with the local PD, fight the zombies on the streets, Carlos and Yuri almost get bitten by a zombie, but they are saved by their 3rd member. Right after that we see a sign reading "Pizza Pizza" which is the largest pizza company in Ontario, Canada. There are no locations in the US.
Visible crew/equipment: In the scene where Nikolai is bitten and the horde bears down on the police and S.T.A.R.S., you can see some crew members and a floodlight. (00:29:35)
Deliberate mistake: When Jill and Angela are in the cafeteria, and the first dog comes running at Jill, if you look closely, you can see Jill bounces back with impact before the dog actually hits her.
Deliberate mistake: In the scene where they're on the airplane, and the bomb has just been landed, there's a sharp instrument that's loose and starts going towards Angela, and Alice takes the fall. If you watch closely, the sharp instrument is aiming towards Alice's right shoulder, but ends up meeting her stomach.
Plot hole: In the school building, Nikolai is mauled by the police dogs that were affected by the T-virus. We see him lying dead on the ground several minutes after the attack and he still hasn't become a zombie. However, when someone dies they almost instantly come back.
Answer: The newspaper clippings we see in her apartment at the start refer to a 'mansion incident' - this in fact relates to the events of the first Resident Evil game, when Jill and other STARS members were trapped in a mansion overrun with the T-Virus. By the end of the game Jill knows exaclty what the T-Virus is and what its effects are.
Even though it mentions it in the newspaper clippings in the movie she wasn't even at the Mansion so therefore she wouldn't have known about the t-virus in the movie.
She was at the mansion prior to the events of Apocalypse, and one of the first ones to know about the virus before it hit Raccoon City.